The future perfect tense is formed with will have + past participle, as in, "I will have left by tomorrow" or "They will have been friends for a long time." The form stays the same no matter what subject you use.

We use the future perfect tense to talk about an action that will be completed sometime in the future. Usually this action will be completed before something else happens or by a certain time in the future. For example, we can say, "I will have graduated by the time I turn 18." This means that I will turn 18 in the future, and at some point before then, I will graduate in the future.

Here are some more examples of sentences using the future perfect tense:

He will have left by the time you get to his house.
Clarissa won't have finished getting her hair done by noon.
We will have been married for one year in October.Will you have finished eating dinner by the time I arrive?